Memory effect on solution crystallization of high molecular weight poly(ethylene oxide)
Memory effect on solution crystallization of high molecular weight poly(ethylene oxide)
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DOI：
10.1016/j.polymer.2012.06.012
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发表时间：
2012-07
期刊：
影响因子：
4.6
通讯作者：
Yun-shu Zhang;Lu-Wei Zhong;Shuang Yang;D. Liang;E. Chen
中科院分区：
文献类型：
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作者：
Yun-shu Zhang;Lu-Wei Zhong;Shuang Yang;D. Liang;E. Chen
本文研究了高分子量聚氧化乙烯（PEO）（400 k，分子量为4 × 105 g/mol）在乙醇中的溶液结晶行为。0.02至2重量%）。采用差示扫描比色法、小角X射线散射法和溶液光散射法跟踪了PEO 400 k的溶解过程。估计了PEO 400 k晶体完全溶解的溶液的实际溶液温度（Tsexps）。与从充分高于Tsexp的溶解温度（Td）冷却的溶液相比，在Tsexp附近的Tds下制备的溶液的结晶动力学快得多。该Tdis越低，在恒定的等温结晶温度下结晶发生得越快。此外，对于Td> Tsexp的溶液，延长溶解时间可显著减缓结晶动力学。实验结果表明，高分子量聚氧化乙烯的溶液结晶具有一定的记忆效应，与本体结晶相似。由于PEO 400 k在Td> Tsexp时可以完全溶解，我们认为溶液结晶也可以具有一种超越传统自晶种效应的记忆效应。这种记忆可能与PEO链在溶解后的松弛有关。很可能，新溶解的链的拓扑结构暂时保留了较少纠缠的链段，这可以促进随后的结晶。对于含有2wt%PEO 400 k的溶液，这种记忆效应的持续时间可长达数小时。
We investigated the solution crystallization behavior of a high molecular weight (MW) poly(ethylene oxide) (PEO) (PEO400k, MW of 4 × 105g/mol) in ethanol with the concentrations ranged from dilute to semi-dilute (i.e., from 0.02 to 2 wt %). We followed the dissolving process of PEO400k using differential scanning colorimetry, small-angle X-ray scattering and solution light scattering. The practical solution temperatures (Tsexps) of the solutions, where the PEO400k crystals were fully dissolved, were estimated. In comparison with that of the solution cooled from a dissolving temperature (Td) sufficiently higher than the Tsexp, the crystallization kinetics of the solutions prepared at Tds in the vicinity of Tsexpis much faster. The lower this Tdis, the faster the crystallization takes place at a constant isothermal crystallization temperature. Moreover, for the solutions with Td> Tsexp, prolonging the duration time of dissolving can significantly slow down the crystallization kinetics. The experimental results indicate that the solution crystallization of high MW PEO bears some memory effect, similar to that observed in bulk crystallization. As the PEO400k can be completely dissolved at Td> Tsexp, we consider that the solution crystallization can also have a type of memory effect beyond the traditional self-seeding effect. This memory may be related to the relaxation of PEO chains after they are dissolved in solution. Probably, the topological structure of the freshly dissolved chains temporarily retains the less entangled segments, which can promote the subsequent crystallization. For the solution with 2 wt % PEO400k, the erasion time of this memory effect could be several hours long.